From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.mainlining.org (mail.mainlining.org [5.75.144.95]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18D87518142; Thu, 17 Sep 2026 16:38:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=5.75.144.95 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789663132; cv=none; b=L9a8owRfa6D8/K7Zr/XVXWy4IpGFnjb4R+5Ge+QJglFBYIzmPBlKw38/jDYh949EXGvtvZRirIHzNkoZk6AeilkDxNVaTtsseY6bH9mzI4H52mMXCiFHpjt6PMjL4WXwR+QCxVL163sMe7R/Uonp+AUasRy3nL6HiqFQhJdmdiI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789663132; c=relaxed/simple; bh=yQbHi2/qjWQm7R28Ag7bKayxGrtMhrNYW+yci+1KRH8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=vFZUqKyBQaxFjJtHwgS0ML9hL8Z5HYTSQZLRFlITsxZ81V6TvuyegGgh+FMVzWmGWSf5L0AA0Km81iJDe6B1Y7CESh3OtcjM5YM00pO+Ywf5bbd1/4mrzv7gClTssUMI4eJlZ/HkCO1m+bCeRae5hQX1F+vkA98slXyRZHx0uzI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org; spf=pass smtp.mailfrom=mainlining.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=fyB1YvSK; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=aqA1APFo; arc=none smtp.client-ip=5.75.144.95 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mainlining.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="fyB1YvSK"; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="aqA1APFo" DKIM-Signature: v=1; a=rsa-sha256; s=202507r; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Date:Subject:To:From; t=1789663111; bh=ghYvDCJ6wWgl/DWKvRlZLjc r4JmsCO6Diem7VtlYvoo=; b=fyB1YvSKvGg1LWKCQZhUBc492tVVzKUf+KZBnI5LNuvCJ5g+ZU E6bkZfZWBE+ZQIYJNva6H1UqybZAs2u6MSsWz7m3aJKEZMUommjJq2vgXFTYVszJusLk7IevwrV 3uAVll3tWQSPCu8psXyYvDa346sjiFeMpOTxP5FVJ2OXn8ivF7Ar9zMblkFo0Sc1qIgzQTEoMnz eECEFt8PMgT7hUncGGx7FjraHbNbzdqgoitO2DlTK+xF0xBeNMnkBZrDOGfDZLxGj/YwQIn8g2u k6hg6hp3BRJs3diJxFQC1cKrT8U/XjrLCX9avh/i1pVEwYhevJmc5z5MoF9+JtxIuPA==; DKIM-Signature: v=1; a=ed25519-sha256; s=202507e; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Date:Subject:To:From; t=1789663111; bh=ghYvDCJ6wWgl/DWKvRlZLjc r4JmsCO6Diem7VtlYvoo=; b=aqA1APFosR9li9xYj4aOMoBwNnHa27+/AJWqeXDYbSCs4I8uW1 aFOhtFdK/xx/jVETv72FWV94mClzvdy8f5Bg==; From: Bradley Morgan To: Andrew Morton , Vineet Gupta , Guo Ren , Yoshinori Sato , Rich Felker , Chris Zankel , Max Filippov Cc: Arnd Bergmann , "Paul E . McKenney" , David Laight , John Paul Adrian Glaubitz , linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Bradley Morgan Subject: [PATCH v3 4/5] sh: Emulate two-byte cmpxchg Date: Thu, 17 Sep 2026 16:38:29 +0000 Message-ID: <20260917163830.3748-5-brads@mainlining.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260917163830.3748-1-brads@mainlining.org> References: <20260917163830.3748-1-brads@mainlining.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit SH has no byte or halfword atomic memory operations, so the __cmpxchg() switch routes case 1 through cmpxchg_emu_u8() and lets case 2 fall through to __cmpxchg_called_with_bad_pointer(), which is declared but never defined, so a two-byte cmpxchg() fails at link time. Route case 2 through the new cmpxchg_emu_u16(), which takes the old and new values as unsigned long, so the (unsigned long) casts move off the call and into _old_ and _new_ declarations that type check the old and new arguments against *ptr through (unsigned long)(0 ? *ptr : _o_), the idiom David Laight suggested, so cmpxchg(&p, 4, 5) no longer compiles silently. Acked-by: John Paul Adrian Glaubitz Signed-off-by: Bradley Morgan --- arch/sh/include/asm/cmpxchg.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h index 1e5dc5ccf7bf..b87f59107b4e 100644 --- a/arch/sh/include/asm/cmpxchg.h +++ b/arch/sh/include/asm/cmpxchg.h @@ -59,6 +59,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old, switch (size) { case 1: return cmpxchg_emu_u8(ptr, old, new); + case 2: + return cmpxchg_emu_u16(ptr, old, new); case 4: return __cmpxchg_u32(ptr, old, new); } @@ -70,8 +72,10 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old, ({ \ __typeof__(*(ptr)) _o_ = (o); \ __typeof__(*(ptr)) _n_ = (n); \ - (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \ - (unsigned long)_n_, sizeof(*(ptr))); \ + unsigned long _old_ = (unsigned long)(0 ? *ptr : _o_); \ + unsigned long _new_ = (unsigned long)(0 ? *ptr : _n_); \ + (__typeof__(*(ptr))) __cmpxchg((ptr), _old_, \ + _new_, sizeof(*(ptr))); \ }) #include -- 2.47.3